The study aims to investigate immunomodulatory effects of thrombopoietin-receptor Agonist (TPO-RA) in patients with primary ITP, who failed first-line therapy or who became intolerant to it. It is hypothesized that the early phase of this autoimmune disease may exhibit a stronger immunomodulatory potential in response to a stimulus, such as romiplostim. Such a process may subsequently be capable to induce regulatory mechanisms or tolerance.